石油类污染场地地下水抽水过程水质变化成因

ANALYSIS OF GROUNDWATER QUALITY CHANGING IN PETROLEUM-CONTAMINATED SITE DURING PUMPING

在某石油类污染场地抽水试验过程中对地下水五项常规水质指标进行了连续监测.通过对指标的相关性和主成分分析,基于抽水、弥散试验,揭示了该场地抽水过程中水质变化的原因,探讨了以水质指标描述石油类污染场地地下水净化的方法.结果显示,水质变化是由昼夜水温变化、抽水和生化耗氧作用三者引起.其中,水温变化是由昼夜变化引起;电导率减小是抽水作用使导电粒子减少的结果;溶解氧(DO)主要受生化耗氧作用和水温引起的氧溶解度变化的影响;pH受水温引起的水的离子积常数变化、抽水作用引起的酸碱性物质减少和生化耗氧作用产生CO2的影响;氧化还原电位(ORP)受抽水作用引起的反应物质浓度减少和水温变化引起的地下水即时溶解氧变化的影响.其中,pH与DO的关系主要是生化耗氧作用的直接结果.温度、电导率、DO、pH和ORP五项指标可提取为地下水自净速率和净化能力两个主成分,描述地下水净化.

Five conventional indices of groundwater quality were monitored continuously in a petroleum-contaminated site during a pumping test.Based on the pumping and dispersion test,the causes of changes in water quality in the site were revealed through correlation and principal component analyses,and a method of describing the purification of petroleum-contaminated groundwater was discussed.The research shows that the changes in groundwater quality are the combined results of day-and-night water temperature change,pumping effect and bio-chemical oxygen effect.The water temperature change results from Day-and-Night change;The reduction of conductivity arises from decreased conductive particles caused by pumping effect;DO change is mainly affected by bio-chemical oxygen effect and oxygen solubility variation due to temperature change;pH varies with water ionic product constant change caused by water temperature,acid-base substance decrease by pumping effect and CO2 production by bio-chemical oxygen effect;ORP is affected by low concentration of reactant caused by pumping effect,and instant DO change by temperature change.The relationship between DO and pH is greatly influenced by the bio-chemical reaction.The five indices（temperature,conductivity,DO,pH and ORP） can be considered as two principal components of self-purification rate and purification capability to describe the purification of groundwater.